Carbureted emissive electrode



the carbide layer is asfollows:

Patented Sept 22, 1942 UNIT/ED STATE SPATENT OFFICE CARBURETED EMISSIVE ELECTRODE- Jean Baptiste Joseph Marcel Abadie,

Puteaux, France v No Drawing. Application January 22, 1940,

Serial No. 315,018

1 Claim. (011176-126) This invention is directed to electrodes for dischargetubes and a method or making them.

More specifically, the invention relates to the production of activated electrodes comprised generally of a metal support containing an electron emissive coating.

Briefly, the present invention is predicated upon the employment or a carbureted alkaline earth metal or salt as an electron emissive electrode coating. Such electrodes act suitably either as anodes or cathodes, and ithasbeen disaiter carbonization. For instance. a mixture made or approximately equal parts of graphite and sugar is suitable, with enough water added to obtain a syrupy composition. After the electrode has been dipped in the graphitic mixture it is allowed to dry slightly and it is then heated in a flameso that the sugar is carbonized and the water evaporated.

A single coating operation in place of the double coating operation may be followed it desirous.

:For example, the conductive support may be covered that the carbon which enters into the t I constitution of the electrodes imparts to them thethermic inertia'necessary to their proper operation as cathodes. Typical spot formations seen frequently on the glass walls of tubes or lamps filled with mercury vapor after continued I operation do not occur when theelectrodes oi the present invention are employed in such tubes. The electrodes furthermore are suited particularly for use in the quantity production of gaseous discharge tubes, sodium lamps, luminescent rare gas tubes operating upon either high or low voltages, or relatively, high pressure metallic vapor lamps. i

In the practice 01 the present invention, an

electrical conductive support is employed for carture exceeds this range there is danger of volatilization or the coating material applied toit. The primary purpose in drying the coating is to harden it upon its support. I p

The metal support may be dipped once, or a number or times it a coating or increased thickness is desired. It 'is recommended that each layer or coating be dried and hardened in order that a layer or increased thickness cumulatively be built upon the support material Alter a coating or the desired thickness has been obtained upon the metal support, the electrode next is dipped into a mixture containing graphite or finely divided carbon.

to 40% by.

The carbon with the emissive metal in the form or a coating be higher than that of adullred; it the temperatreated once or a number or times and dried, as described, in a mixture comprised of approximately of a mixture 01 equal partsof graphite and sugar and V; or a mixture or lime and baryta, enough water again being used to provide a sludge or syrup sufiiciently fluid to facilitate the application of the coating to the support. i

The alkali or alkaline earth carbides are formed in the electrode during the pumping operation.

In this way the carbon enters tion of the electrode.

into the constitu- During the pumping operation thepresence or the carbon causes an extremely rapid production or the emissive salts used. For instance, in a typical operation a current is passed through the tube during the period that it is being pumped, the salts are reduced, carbides are formed and the electrodes arepurified and ready for usage in the tube inwhich they are to be contained.

In place of the lime and baryta used for constituting the electrode other alkaline earth salts may be employedeither alone or in conjunction with alkali metal salts.

The carbon contained in the electrodes has a veryhigh anodic drop in rare gases as well as in metallic vapors.

The electrodes are characterized particularly in that carbon in the powdery term is associated over the electrically conductive support, and in that the electrodes so constituted may be used indiiierentl as cathodes or anodes in gaseous discharge tubes.

Having described my invention, I claim:

An electrode for a discharge'tube which is characterized in that it may be used indifierently as a cathode or an anode and which is comprised or graphite may either be held in suspension or may be in such mixture as to produce a coating of an electrically conductive support containing a coating comprised of an emissive material selected from the group consisting oi. alkaline earth metals and alkaline earth salts intimately associated with powderedcarbon which is physically present as tree carbon.

JEAN BAPTISTE JOSEPH I MARGEL mama, 

